Not all methyl bonds are harmful to the liver. We put all kinds of compounds in and on our bodies every day that are methylated in some way. Caffeine is a methylxanthine and there aren't millions of Americans dropping dead from their daily cups'o joe.

It's when a STEROID molecule is methylated that the detrimental effects can occur on the liver.

It's not actually the methylated compound that causes the harm, but the compounds that the 17 alpha alkylated steroid breaks down into. These are called 17-glucuronide metabolites. The way the body metabolizes these is what causes harm to the liver.